The present invention relates to a thrust reverser for a turbofan engine, more particularly such a thrust reverser having an inherent safety feature to prevent inadvertent opening of the thrust reverser door.
Turbofan engines are well known in the art and typically comprise a turbojet engine drivingly connected to a turbofan, usually mounted on the front of the turbojet engine. A turbofan housing, radially displaced from, but generally concentric with respect to the turbojet engine housing defines a cold flow air duct for air driven by the turbofan. In such a turbofan engine having a relatively high bypass ratio, thrust reversers are typically provided on the turbofan housing so as to redirect the air passing through the cold flow air duct during landing of the aircraft in order to provide a reverse thrust.
Thrust reversers may assume many different types, but a typical thrust reverser is illustrated in FIG. 1. The thrust reverser comprises a stationary, upstream portion 1 which forms a part of the turbofan housing, a movable portion 2 which redirects the air passing through the cold flow air duct and a stationary, downstream collar 3 which also forms a downstream portion of the turbofan housing. The stationary, upstream portion 1 typically comprises an exterior panel 4 which defines a portion of the exterior surface of the turbofan housing, an interior panel 5 which, in conjunction with the housing for the turbojet engine (not shown) defines the boundaries of the cold flow air duct and a frame 6 which interconnects panels 4 and 5. The frame 6 also supports an actuator 7a for controlling the movement of the movable portion 2, which in this instance comprises one or more movable thrust reversing doors 7. The number of such doors may vary depending upon the application of the turbofan engine to a particular type of aircraft and typically comprises 2, 3 or 4 such thrust reverser doors. These doors may be displaced around the circumference of the turbofan housing and, when in their deployed positions redirect the air passing through the cold flow air duct to provide the thrust reversing effect.
FIG. 2 illustrates a pair of such thrust reversing doors 7 in their deployed positions in which the forward, or upstream, edges are displaced radially outwardly from the generally annular turbofan housing. As is well known in the art, rear, or downstream, portions of the thrust reverser doors 7 extend inwardly into the cold flow duct so as to redirect the air outwardly through the turbofan housing and in a forward direction. Each such thrust reverser door 7 is operatively associated with a hydraulic jack or actuator 7a, which typically comprises a cylinder having an extendible and retractable piston rod attached to the thrust reverser door 7.
Such thrust reversers are well known in the art and typical examples of which may be found in U.S. Pat. Nos. 4,894,985; 4,858,430; 4,916,895; 4,914,905; 4,976,466; 4,960,243; and 5,039,171.
These types of thrust reverser doors have proven very effective in providing thrust reversing forces to the air frame with which the turbofan engine is associated. However, serious problems may arise if the thrust reverser doors are deployed at an inappropriate time. Accidental initiation of thrust reversal can cause catastrophic results to the aircraft and a number of devices are known to preclude such accidental deployment of the thrust reverser doors. In particular, a mechanical locking device on the thrust reverser door and the support structure are known, as well as a mechanical locking device on the thrust reverser control actuator. In some applications, however, such dual safety devices may be inadequate to preclude all risk of malfunctions, especially when the thrust reverser doors are strongly urged to move to their deployed, reverse thrust positions by normal forces acting on the doors.